Deok-Rae Cho

Three-dimensional Unstable Detonation Wave Structures in Pipes

Three-dimensional structures of detonation wave propagating in tubes were investigated. Inviscid fluid dynamics equations coupled with a conservation equation of reaction progress variable were analyzed by a MUSCL-type TVD scheme and four stage Runge- Kutta time integration. Variable-γ formulation was used to account for the variable properties between unburned and burned states and the chemical reaction was modeled by using a simplified one-step irreversible kinetics model. The computational code was parallelized based on domain decomposition technique using MPI-II message passing library. The computations were carried out using an in-house Windows cluster system with AMD AthlonTM XP and AthlonTM 64-X2 processor cores. The computational domain consisted of through a square-shaped duct with wall conditions on its lateral boundaries. As an initial condition, analytical ZND solution was distributed over the computational domain with small disturbances. The unsteady computational results in three-dimension show the detailed mechanisms of rectangular and diagonal mode of detonation wave instabilities resulting same cell length but different cell width in smoked-foil record.

Performance Estimation of Hydrazine-based PDEs for Spacecraft Applications

The pulsed operational characteristics of PDE (Pulse Detonation Engines) would be quite useful for the reaction control system (RCS) of the spacecraft, for which the most of the operation is held at the pulsed mode. Storable propellants are preferable for the long term use. Mono-propellants feed into a catalyst bed in a thrust chamber where it decomposes catalytically and thermally to create a hot gas that is exhausted through nozzle. Hydrazine is the most common liquid mono-propellant for spacecraft propulsion due to low system complexity, relatively low cost and good storability. In the present study, an accurate performance prediction package is developed by using a Fortran program of Endo theory and combining with NASA Chemical Equilibrium which Application (CEA) code. The PDE performance is estimated by passing the solutions of Chapman-Jouguet (CJ) detonation from the CEA code to Endo theory program with predicts the expansion process inside the PDE tube by the compressible flow theories. A PDE database for hydrazine is constructed by operating the package over a wide range of initial condition

Optimization of LU-SGS Code for the Acceleration on the Modern Microprocessors

An approach for composing a performance optimized computational code is suggested for the latest microprocessors. The concept of the code optimization, termed localization, is maximizing the utilization of the second level cache that is common to all the latest computer systems, and minimizing the access to system main memory. In this study, the localized optimization of the LU-SGS (Lower-Upper Symmetric Gauss-Seidel) code for the solution of fluid dynamic equations was carried out in three different levels and tested for several different microprocessor architectures widely used these days. The test results of localized optimization showed a remarkable performance gain of more than two times faster solution than the baseline algorithm for producing exactly the same solution on the same computer system.

Detonation Wave Simulation of Thermally Cracked JP-7 Fuel/Oxygen Mixture using Induction Parameter Modeling

The detonation wave characteristics of JP-7 and oxygen mixture is investigated by one-step induction parameter model (IPM) obtained from a detailed chemistry mechanism. A general procedure of obtaining reliable one-step kinetics IPM for hydrocarbon mixture from the fully detailed chemistry is described in this study. The IPM is obtained by the reconstruction of the induction time database obtained from a detailed kinetics library. The IPM was confirmed by the comparison of the induction time calculations with that from detailed kinetics. The IPM is later implemented to a fluid dynamics code and applied for the numerical simulation of detonation wave propagation. The numerical results show the detailed characteristics of the detonation wave propagation in JP-7 and oxygen mixture at affordable computing time, which is not be possible by the direct application of the detailed chemical kinetics mechanism of hydrocarbon fuel combustion.